Which initiator tRNA carries the initial amino acid in bacteria?

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Multiple Choice

Which initiator tRNA carries the initial amino acid in bacteria?

Explanation:
In bacterial translation, the first amino acid to enter the growing chain is formyl-methionine. This is delivered by a special initiator tRNA charged with methionine and then formylated to become formyl-methionine tRNA (fMet-tRNAfMet). The initiator tRNA pairs with the start codon (AUG) at the start site of the ribosome, a process guided by initiation factors, and it is this formylated methionine that starts every bacterial protein. The other aminoacyl tRNAs—valine, leucine, and isoleucine—are used during elongation to incorporate their amino acids at internal positions after the start codon has been established. The formyl group on the initiating methionine helps distinguish the initiator tRNA from elongator tRNAs and ensures correct initiation. After initiation, the formyl group is typically removed later in processing, while the methionine can be retained or removed depending on later steps.

In bacterial translation, the first amino acid to enter the growing chain is formyl-methionine. This is delivered by a special initiator tRNA charged with methionine and then formylated to become formyl-methionine tRNA (fMet-tRNAfMet). The initiator tRNA pairs with the start codon (AUG) at the start site of the ribosome, a process guided by initiation factors, and it is this formylated methionine that starts every bacterial protein.

The other aminoacyl tRNAs—valine, leucine, and isoleucine—are used during elongation to incorporate their amino acids at internal positions after the start codon has been established. The formyl group on the initiating methionine helps distinguish the initiator tRNA from elongator tRNAs and ensures correct initiation. After initiation, the formyl group is typically removed later in processing, while the methionine can be retained or removed depending on later steps.

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